Thermal decomposition kinetics and mechanism of magnesium bicarbonate aqueous solution

Thermal decomposition kinetics and mechanism of magnesium bicarbonate in aqueous solution were investigated. Decomposition rate function, f(η) = 1 − 2/3η − (1 − η)2/3, was found to fit well with Ginstling–Brounshtein's diffusion model. The good linearity relationship of rate equation 1 − 2/3η − (1 − η)2/3 against time further validated that decomposition process of magnesium bicarbonate was partially controlled by the mode of diffusion. The apparent activation energy was calculated to be 47.05 kJ/mol, indicating that the overall decomposition process was also controlled by chemical reactions. The kinetic model was in good agreement with the experimental results. The effect of stirring speed, system temperature and the concentration of Mg2+ in Mg(HCO3)2 aqueous solution on decomposition ratio was analyzed. The decomposition ratio reached 88% at 50 °C. The formed basic magnesium carbonate was of microsphere structure. The mechanism of thermal decomposition of Mg(HCO3)2 was proposed in this paper.